Process of treating leather and product



Oct.15, 1940. J. H. MCGILL" 2,217,961

PROCESS OF TREATING LEATHER AND PRODUCT Filed Aug. 9', 1937 PatentedOct. 15,1940

UNITED STATES PnocEss or TREATING LEATHER AND raonuc'r John H. McGill,Winchester, Mass, assignor to B. B. Chemical 00., Boston, Mass, acorporation of Massachusetts Application August 9, 1937, Serial No.158,017

1 Claim. (01- 36-34) This invention relates to leather and leatherarticles of advantageous properties and to methods of preparing thesame.

Objects of this invention are to provide leather 5 articles of improvedcharacteristics, including stiffness, wearability, resistance tofraying, and resistance to detanning upon exposure to water, while'inother respects having essentially the 7 normal characteristics ofleather. Another ob- 10 ject is to provide leather articles wherein theflesh side of the leather and adjacent portions are improved in suchrespects, while preserving the grain side of the leather in its originalcondition. Other objects are to provide advantageous methods ofpreparing such articles.

In accordance with the above and other ob jects, the invention, in oneof its aspects, resides in leather articles wherein leather isimpregnated from the flesh side with' molten thermoplastic materialselected from the general group consisting of waxes and resins andwherein said im-,, pregnation has taken place to a predetermined degreeapproaching but not reaching the grain side thereof. As a practicalmatter, the leather or leather articles have the moisture content ofair-dry" leather, that is, leather containing the moisture content ofleather subjected to the I atmosphere. In such leather articles theflesh side of the article remains firm and stiff through- 80 out thelife thereof. The invention makes possible the use of so-called fleshyleather for many purposes hitherto impossible by reason of the soft,yielding and unsubstantial properties of the flesh side of such leather.As a result of this 35 invention, such leather may be treated to provideproperties of firmness and stiffness equal to those of leathers ofconsiderably higher quality. In the case of high quality leather, theinvention may be employed greatly to improve the i properties of theleather for many purposes.

A highly advantageous application of the above aspect of the inventionis in the preparation of detachable heel lifts such as disclosed, forexample, in United States 'Letters Patent No.

45 1,844,248, granted February 9, 1932, in the names of Frank T. Gentileand Fred Maccarone. In-

such constructions, a leather heel lift is detachably disposed with theflesh side thereof contiguous to the lift-receiving surface of a wood 60heel and the lift is secured to the heel by means of a post extendinginto and secured in a socket in the heel. When the lift is worn, removalthereof is ordinarily accomplished by first inserting a leverage toolbetween the flesh side of 71 the lift and the adjacenttop-lift-receiving surface of the wood heel. By the present invention,heel lifts may be prepared wherein the flesh side of the leather andadjacent portions are stiifened and harde'ned,-and which lifts when wornsufliciently for replacement readily may be 5 pried off the wood heeland removed, the hardened flesh surface of the leather providing asubstantial bearing surface for the removing tool. Moreover, duringwear, such lifts exhibit substantially no fraying at the treatedportions 10 thereof.

Another aspect of this invention involves a process of impregnatingleather from the flesh side with a molten thermoplastic selected fromthe general group consisting of waxes and resins. This may beaccomplished by mechanicallysupporting the leather, flesh side downward,at a predetermined depth in a bath of such molten thermoplasticmaterial. A wax alone, or a resin alone, may be used, or two or morewaxes, or 20 two or more resins, or a mixture or blend of waxes andresins. The temperature of the bath is maintained at a point suflicientto insure speedy penetration, and ordinarily is within the range of 115C. to upwards of 140 C. The time of 2s immersion of the leather isdependent upon the desired degree of penetration andupon the temperatureof the bath and should be sufdciently short'so as not to destroy thefibrous structure a and the identity of the leather. The hotter the bathof-molten material, the shorter will be the time required to accomplisha specific degree of penetration. At a given temperature, the longer theimmersion in the molten material, the greater will be the penetrationinto the leather.

- In another aspect, this invention relates to leather articles theentire exterior surfaces of which, including the grain surfaces, areimpregnated to a predetermined degree with molten thermoplastic materialselected from the general group consisting of" waxes and resins. Heellifts of this character may be prepared. Another important example ofthis. type of article is found in leather gaskets such as employed infire hydrants. Leather fire hydrant gaskets con- 4 templated by thisinvention possess considerably longer life than the gaskets hithertoused, due in part tothe fact that the gaskets of this invention exhibitconsiderably greater resistance to the detanning action of the water towhich they are exposed. Valve sticking is greatly reduced due to alessened corrosive effect upon the metallic valve seats with which thegaskets cooperate. Furthermore, due to their waterproof character,gaskets so treated resist the swelling, distorting speaking, suchgaskets exhibit generally better wearing properties under the difficultconditions to which they are subjected.

This invention further contemplates a method of preparing articlesimpregnated throughout their exterior surfaces with molten thermoplasticmaterial selected from the general group consisting of waxes and resins,for example, fire hydrant gaskets. Such method involves completeimmersion of such articles in the aforementioned thermoplastic materialat a temperature and for a time sufficient to accomplish the desiredimpregnation.

In the drawing,

Fig. 1 is a diagrammatic vertical sectional view of impregnatingapparatus illustrating the impregnation of leather from the flesh sideand edges by supporting the leather to a predetermined degree below thesurface of molten wax or resin;

Fig. 2 is a diagrammatic vertical sectional view of impregnatingapparatus illustrating the impregnation of a leather fire hydrant gasketthroughout its exterior surface;

Fig. 3 is a perspective view, partially broken away, of a' leather heelliftimpregnated with .molten wax or resin from the flesh side and edges,the impregnation extending toward, but not reaching the grain side ofthe leather lift; and

Fig. 4 is a perspective view of a leather fire hydrant gasket treated inaccordance with this invention.

With respect to the impregnation of leather on its flesh side theinvention may be carried out by immersing the leather to a predetermineddepth in a bath of molten thermoplastic ma terial selected from thegeneral group of waxes and resins. Thus, by way of specific example andreferring to Fig. 1, the tray [6 contains a removable holder l8 withspaced horizontal surfaces 20 arranged to carry leather stock, such asthe heel lift 22. The tray I6 contains molten thermoplastic material 26,specifically, in this example, carnauba wax, maintained at a temperatureof about to C. A leather heel lift 22 of ordinary vegetable-tanned solestock and containing the ordinary amount of moisture of leather whichhas been exposed to the atmosphere, namely, air-dry" leather, and havinga thickness of about %8' of an inch, was supported on the surfaces 20with the grain side 26 thereof above the surface of the carnauba wax 24and with the flesh side 28 down and immersed in the wax 24. The leatherlift 22 was allowed to remain in contact with the carnauba wax.24 forabout 3 minutes during which period bubbles of air and moisture appearedin the wax 24 in the vicinity of the lift 22. The lift 22 was thenremoved from the bath 24. After removal of the lift 22 from the bathnearly all of the excess wax on the edges l2 and the flesh side 28 waswiped off by means ofa cloth. Remaining traces of wax appearing on thesurfaces 28 and I2 of the leather'were caused to disappear into the.

' terial.

moved therefrom while the holder I8 remains in the molten bath, or theholder 18 may be redescribed above was impregnated as indicated at Mwith carnauba wax to about one-fourth of its thickness from the fleshside 23. Penetration to a like extent had taken place from the edges H2.The impregnated portion I 4 was relatively hard and stiff and free fromany tendency to fray. The grain side 26 and the major portion of thesubstance of the lift was in its original condition and free from theimpregnating ma- The edges l2 of the leather lift 22 were found toreceive leather finishes and polishes in a very satisfactory manner andto give results equal to, or even better than, ordinary leather undersimilar conditions. Moreover, the treated lift 22 was found to exhibitsuperior properties when used in association with a detachable heelconstruction, such as shown in the Gentile and Maccarone Patent No.1,844,248. Thus, the metal prongs of a post of a detachable heelconstruction, such as shown in the patent above mentioned, were readilyincorporated into the substance of the lift 22 from the flesh sidethereof to form a secure mechanical attachment. Moreover, uponapplication to a shoe heel as part of such a detachable heelconstruction, lifts treated in the manner of thisv invention exhibitedsubstantially no fraying in those portions thereof which had beenimpregnated with the wax. Furthermore, the flesh side 28 retained 'itshardness and firmness through the life of the lift, thereby providing afirm bearing surface for removal of the lift when worn. It has furtherbeen found that leather lifts treated in the manner above describedresist the detanning action of water to a far greater extent thanleather not so treated.

The use in a detachable heel construction of a leather lift prepared inaccordance with this invention is disclosed and claimed in my copendingapplication, Serial No. 158,016, filed August 9, 1937 (now Patent No.2,189,811, granted February 13, 1940).

In the above specific example, I have illustrated the practice of theinvention with carnauba wax. The same procedure, times, and temperatureshave been followed in carrying out the impregnation with cumar resin,and with a mixture of 60% montan wax and 40% M rosin. (The M" refers toU. S. Department of Agriculture classification.) Results were obtainedequivalent to those obtained with carnauba wax, and as described above.

In carrying out the invention, various waxes, resins, and mixtures orcombinations thereof may be employed; Examples of suitable materialswhich may be used singly or in combination are as follows: candelillawax, carnauba wax, montan -wax, Rangoon wax, ozokerite, black ozokerite,

' maybe varied through a reasonably. wide range and may be controlled inany suitable manner,

contained in the leather.

.will depend upon the depth of penetration or imalthough the temperaturepreferably remains below about 150 C. in order to prevent destruction ofthe fibrous structure of the leather and to pre-' vent possibleexplosive evaporation of moisture The time of immersion pregnationdesired and upon the temperature of the molten wax or resin. I havefound that suitable periods of immersion will range, from about 30seconds in the case of a wax or resinbath having a temperature in theneighborhood of 140 C.

' to about 20 minutes in the case of wax or resin at a temperature about115 0. Between these extremes, by way of example, at a temperature ofabout 125 C., an immersion time of 3 to 5 minutes was found suitable inthe case of molten baths of #3 carnauba wax, or yellow ozokerite, orcumar resin, or a combination of 60% bleached montan wax and 40% Mrosin. The time'of immersion and temperature of the wax or resin bath isdependent upon the nature of a particular leather to be treated and inpart upon the moisture content thereof. It is well to keep thetemperature of the bath as low as possible but it should be high enoughso that bubbles of air and wax or resin. a

By varying the depth of immersion of the leather in the wax or resinbath, the characteristics of the impregnation may be varied. Thus, if atop lift of leather. similar to sole stock is immersed in a wax or resinbath, flesh side down, to an extent that only the grain surface remainsout of the bath, the impregnation of the wax or resin will take placesimultaneously from the edges of the lift (II-Fig. 3) as well as fromthe bottom thereof (IL-Fig. 3). After a relatively short period ofimmersion, therefore, the result will be substantially a case hardeningeffect on the edges and flesh side of the leather, the grain side andthe major portion of the substance of the heel being free from theimpregnating material. Upon longer immersion .the wax or resin,- aidedby capillary action, tends to penetrate from the flesh side further upthrough the leather and tends to penetrate to a level at least equal tothat of the wax or resin in the bath. If the leather is immersed fleshside down in the wax' or resin to 'onlya slight degree, the penetrationof the wax or resin takes place substantially entirely on the fleshside. In carrying out the impregnation, a piece of leather stock ofsuitable size may be impregnated, and subsequently smaller articles,such as heel lifts, may be died out or cut out of such larger pieces.

Upon removing the leather from the bath it is generally quite easy toremove excess wax or resin by wiping the leather with a cloth. Iffurther removal is necessary, it may be accomplished by scraping,abrading, or by melting the wax or resin and driving it into the leatherby means of a hot airblast maintained above the melting point of thewax, resin, or mixture of waxes and resins used.

In the Figs. 2 and 4, I have illustrated the application of thisinvention to a case whereinit is desired to impregnate a leather articleover its entire surface area. Specifically, I have illustrated a flrehydrant gasket 30 consisting of'a properties.

upon which the gasket 30 may rest upon the bot- 10 tom of the tray",said supporting means being so arranged as to permit the molten wax orresin to contact with the surface of the gasket throughout its extent.With molten waxes or resins, such as carnauba wax, or cumar resin, or amixture of 60% montan wax and 40% M rosin, at a \temperature in theneighborhood of 110 to 125 C., a suitable impregnation may beaccomplished by permitting the gasket 30 to remain in the molten wax orresin for a period of about 5 minutes. 20

The temperature and time of immersion of the gasket 30 in the wax orresin 34 may of course be varied within limits as indicatedhereinbefore. After removal of the gasket "from the molten wax or resinbath :4 any excess wax or resin re- 25 maining on the surface of thegasket may be removed by wiping, scraping or abrading or by means of ahot air blast above the melting point .of the impregnating material.-

A gasket treated in the manner described above has unique propertieswhen employed in a flre hydrant in that the presence of the wax or resinimparts to the gasket the property of resisting the detanning anddeteriorating effects of water to a far greater degree than ordinaryuntreated leather. Such increased resistance to detanning and consequentretention of tannic acid in the leather diminishes the c0rrosive effecton the metal valve seat with which the gasket contacts and consequentlythe occurrence of valve sticking is greatly minimized, if notsubstantially eliminated.

' The aspect of this invention pertaining to the impregnation of aleather article throughout its exterior surface may also be practicedwith respect to a heel lift, in which case the lift is completelyimmersed in a wax or resin bath.

In the practice of this invention, various dyes, miscible or compatiblewith the waxes or resins used, may be added to the mixture. An exampleis the addition of 3 grams of oil black dye to 97 grams of blackozokerite wax. Such impregnating agent imparts not only thepreviously-mentioned advantageous properties to the leather but alsodyes it a permanent black. 1

Having described my invention, what I claim as new and desire to secureby Letters Patent of the United States is:

A detachable leather heel lift arranged for contact by its flesh sidewith a heel, the flesh side and adjacent edges of said lift being casehardened by impregnation by material selected from the general groupconsisting of waxes and resins, whereby the flesh side of the liftexhibits hardness and firmness throughout the life of the lift andprovides a flrm bearing surface for removal of the lift when worn, andthe edges of the lift exhibit substantially no fraying, while the grainside of the lift and the major portion of the substance thereof exhibittheir original leather Join n. McGII-L.

